2. Field of the Invention
This invention is directed to a catalytic converter for removing noxious components from a gaseous stream. More particularly, it is directed to a catalytic converter for use in a gaseous stream, e.g. internal combustion engine exhaust effluent, which comprises cylindrical segments of monolithic ceramic composed of, by way of non-limiting examples, alumina, mullite, cordierite or combinations thereof with one another impregnated with catalytically active materials, such as, for example, hydrocarbon and carbon monoxide oxidation catalysts, axially spaced apart by greater than 1/4 inch with a cylindrical metal container, said container having a gas inlet upstream from said spaced apart segments and a gas outlet downstream therefrom. Further, said metal container is provided with a plurality, e.g. two to about 50 or more, and more preferably from about 6 to about 16, of spaced apart protruding metal fins attached to the outer circumference thereof and over the areas of the metal container exposed to the faces of said segments.
2. Discussion of Prior Art
Monolithic ceramic oxidation catalysts used to date in internal combustion exhaust effluent streams have been melted and otherwise thermally damaged under continuous operation due to heat of reaction when high concentrations of combustibles, such as carbon monoxide, hydrocarbons and hydrogen, are present in the exhaust effluent with oxygen. Although several devices have been proposed in the art to prevent such thermal damage, such as, for example, converter by-pass systems, water injection into the exhaust effluent, shut-off of secondary air and feedback control of air-fuel mixtures, they are usually accompanied by a variety of serious disadvantages, such as very high cost, unreliability, special situation effectiveness limitations, increased emissions and low safety.
The present catalytic converter design allows effective use of monolithic ceramic oxidation catalysts under the severe thermal conditions possible in catalytic treatment of the exhaust effluent of internal combustion engines. The proposed converter effectively decreases the thermal response of a monolithic ceramic converter in the high temperature range (i.e. at 1200.degree. F and above) and increases its effective operating life without incurring any of the above disadvantages other than a fractional increase in cost.
Numerous multi-bed catalytic converters are known in the art for oxidation of gaseous combustibles where the catalytic beds are composed of granular, beaded or particulate catalyst materials, thereby creating problems of catalyst disposition within the converter, especially where use thereof would be in a vibrating or roughly bouncing situation, e.g. in the exhaust system of an automobile which may be used over rough roads. The multiplicity of catalyst beds is primarily for the purpose of increasing conversion of the combustible materials comprised in the gaseous effluent stream being contacted therewith. Examples of such converters are described in U.S. Pat. Nos. 3,540,838; 3,503,715; and 3,409,920 and British Pat. Nos. 1,009,609; 942,841 and 1,034,621.
U.S. Pat. No. 3,186,806 teaches a catalytic apparatus, for use in the exhaust effluent of an internal combustion engine, provided with a series of horizontally disposed catalyst cartridges through which exhaust gases successively pass from top to bottom. U.S. Pat. No. 3,180,712 teaches a complicated two-stage catalytic converter-muffler. Each of these latter two mentioned converters employ catalyst in particle form.